MP3 Diags finds problems in MP3 files and helps the user fix many of them. It looks at both the audio part (VBR info, quality, normalization) and the tags containing track information (ID3). It has a tag editor, which can download album information (including cover art) from MusicBrainz and Discogs, as well as paste data from the clipboard. Track information can also be extracted from a file's name. Another component is the file renamer, which can rename files based on the fields in their ID3V2 tag (artist, track number, album, genre, etc.).
Evolvotron is an interactive "generative art" application to evolve images/textures/patterns through an iterative process of random mutation and user-selection driven evolution. If you like lava lamps, and never got tired of the Mandelbrot set, this could be the software for you. It's implemented using Qt, and is multithreaded.
Kwooty is a .nzb usenet binary grabber for KDE 4. Its main features include multi-server support, smart Par2 download, automatic file verification/repairing and archive extraction (RAR, Zip, 7z), automatic file downloading after opening the NZB file, shutdown scheduling, built-in SSL connection support, queue management, and more.
FatRat is a download manager that is rich in features and is continuously extended. Its features include HTTP(S)/FTP/SFTP downloads, FTP/SFTP uploads, RSS feed support with special functions for TV shows and podcasts, BitTorrent support (including torrent creation, DHT, UPnP, and encryption), torrent searching, Support for SOCKS5 and HTTP proxies, RapidShare.com FREE downloads, RapidShare.com uploads, RapidShare.com link verification and folder extraction, RapidSafe link decoding, MD4/MD5/SHA1 hash computing, remote control via Jabber or a Web interface, and YouTube video downloading.
Qassir is a graphical frontend to manage encrypted folders. At the moment, it only supports mounting and unmounting folders encrypted with EncFS. Future releases will provide access to all of EncFS's functionality, i.e. creation of encrypted folders, changing the password for a folder, etc.
Drumstick is a C++ wrapper around the ALSA library sequencer interface using Qt4 objects, idioms, and style. The ALSA sequencer provides software support for MIDI technology on Linux. Complementary multiplatform classes for SMF and WRK file processing are also included. This library is used in KMetronome, KMidimon, and KMid2 and was formerly known as "aseqmm".